Apparatus and method for programmable spatially selective nanoscale surface functionalization

ABSTRACT

A spatially selective surface functionalization device configured to generate a pattern of micro plasmas and functionalize a substrate surface may include: a pattern management system, a patterning head, and a gas delivery system, wherein the gas delivery system provides a primed gas mixture for forming a plasma between the patterning head and a target substrate below the patterning head. A patterning head may generate a distribution of micro plasmas from individual directed beams of electrons with spatial separation. A pattern management system may store and manipulate information about a pattern of surface functionalization and generate instructions for regulating a distribution of micro plasmas that functionalize a substrate surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent filing is a continuation of U.S. patent applicationSer. No. 15/600,470, titled APPARATUS AND METHOD FOR PROGRAMMABLESPATIALLY SELECTIVE NANOSCALE SURFACE FUNCTIONALIZATION, filed 19 May2017, which claims the benefit of U.S. Provisional Patent Application62/338,955, titled APPARATUS AND METHOD FOR PROGRAMMABLE SPATIALLYSELECTIVE NANOSCALE SURFACE FUNCTIONALIZATION, filed 19 May 2016; U.S.Provisional Patent Application 62/338,996, titled PUMP-FREE MICROFLUIDICANALYTICAL CHIP, filed 19 May 2016; U.S. Provisional Patent Application62/339,002, titled PUMP-FREE MICROFLUIDIC ANALYTICAL SYSTEMS, filed 19May 2016; and U.S. Provisional Patent Application 62/339,008, titledSTAND ALONE PUMP-FREE MICROFLUIDIC ANALYTICAL CHIP DEVICE, filed 19 May2016. The content of each of these earlier filed patent applications ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates generally to methods and apparatus for performingmodification of surfaces of materials. Modification of surfaces mayinclude modifying form and structure of surfaces and modifying thechemical composition of surfaces. Surface modification may be performedusing a plasma.

BACKGROUND OF THE INVENTION

The present disclosure relates to a device for forming a plasma tomodify surface chemistry or functionalization of a material afterexposure of the material to the plasma. Surface chemistry modificationmay include modifying the hydrophobicity of a surface, modifying adimension of the surface, modifying an electrochemical characteristic ofa material, modifying an optical characteristic of a material, ormodifying a dimension of modified area of a surface.

SUMMARY OF THE INVENTION

The invention addressing these and other drawbacks relates to methods,apparatuses, and/or systems for prioritizing retrieval and/or processingof data over retrieval and/or processing of other data.

Aspects of the present disclosure relate to a device for spatiallyselective surface functionalization, comprising a pattern managementsystem, a patterning head, and a gas delivery system, wherein thepatterning head is configured to generate a first distribution of microplasmas against a top surface of a substrate in a gas mixture at leastpartially provided by the gas delivery system. The distribution of microplasmas may be according to a pattern stored in the pattern managementsystem, according to a first portion of the pattern.

Aspects of the present disclosure relate to a method for modifying asurface with a plasma. The method includes operations of energizing afirst set of individually addressable electron emission structures in anelectron source, the electron source having a membrane with a firstsurface and a second surface; and creating a blend of gases in a workingvolume adjacent to the second surface of the membrane on an outersurface of the electron source. The method also includes operations ofaccelerating electrons from the first set of individually addressableelectron emission structures towards the membrane, forming a first setof micro plasmas where the accelerated electrons from the first set ofindividually addressable electron emission structures intersects theblend of gases, and adjusting a distance between a substrate and thesecond surface such that the first set of micro plasmas intersects a topsurface of the substrate at a first location.

Aspects of the present disclosure relate to a method of making a plasmadevice having an electron source that comprises operations of forming,in the electron source, an array of individually addressable electronemission structures on an chip, placing, in the electron source, anelectron accelerating structure between the chip and a target substrate,and interconnecting the array of individually addressable electronemission structures with a power supply and the electron acceleratingstructure. The method also includes operations of placing, in a wall ofthe electron source, a membrane configured to pass a directed beam ofelectrons, positioning a nozzle of a gas delivery system to deliver aflow of gas into a working volume between the electron source and thetarget substrate, and connecting a controller element to the powersupply configured to regulate an electrical potential between the arrayof individually addressable electron emission structures and theelectron accelerating structure.

These and other features of the present invention, as well as themethods of operation and functions of the related elements of structureand the combination of parts and economies of manufacture, will becomemore apparent upon consideration of the following description and theappended claims with reference to the accompanying drawings, all ofwhich form a part of this specification, wherein like reference numeralsdesignate corresponding parts in the various figures. It is to beexpressly understood, however, that the drawings are for the purpose ofillustration and description only and are not intended as a definitionof the limits of the invention. As used in the specification and in theclaims, the singular form of “a”, “an”, and “the” include pluralreferents unless the context clearly dictates otherwise. In addition, asused in the specification and the claims, the term “or” means “and/or”unless the context clearly dictates otherwise. Further, the terms “on”,“over”, “above”, “below”, “beneath”, and “under” may generally be usedto indicate the position of portions of embodiments described hereinalong an axis through the portions, without an absolute reference to aparticular direction. Thus, one portion may be “on” or “above” or“below” or “under” another, even when the portions are rotated withrespect to an external frame of reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example, and not by way oflimitation, in the figures of the accompanying drawing and in which likereference numerals refer to similar elements.

FIG. 1 depicts a cross-sectional diagram of an embodiment of a nanoscalesurface functionalization device;

FIG. 2 depicts a cross-sectional view of an embodiment of apparatus forgenerating micro plasmas using electron emission structures;

FIG. 3 depicts a cross-sectional view of an embodiment of a chip havingelectron emission structures;

FIG. 4 depicts a cross-sectional analysis of an embodiment of anapparatus having electron emission structures;

FIG. 5A depicts a cross-sectional view of an embodiment of a substratepatterned by an electron-emission patterning head by a masklesspatterning method;

FIGS. 5B-5E depict patterns of micro-plasmas generated by aelectron-emission patterning head to form the embodiment of FIG. 5A;

FIG. 6 depicts a flow diagram of an implementation of a method ofgenerating a patterned array of micro-plasmas;

FIG. 7 depicts a flow diagram of an implementation of a method formodifying surface functionalization of a material;

FIG. 8 depicts a plasma device having an array of emission structures ofan electron source substrate; and

FIG. 9 depicts an embodiment of a plasma device having a plurality ofpyroelectric emission structures.

Methods, embodiments, implementations, and apparatus described hereinare merely representative of the invention claimed herein. Accordingly,other methods, embodiments, implementations, and apparatus may also fallwithin the scope of the present disclosure after being envisioned by aperson of ordinary skill in the art.

DETAILED DESCRIPTION OF THE INVENTION

Surface modification during a manufacturing processes can impart newproperties to materials. One method of surface modification includesusing a plasma to modify a chemical structure of the surface. Surfacemodification using plasma tools can provide a rapid, low cost method ofchanging the characteristics of a material surface while retainingcharacteristics of the bulk of the material. For example, a glass orplastic substrate material may have desirable bulk characteristics suchas optical transparency, structural rigidity, or flexibility, but thesurface of the substrate material may not have a desired physical orchemical property such as hydrophobicity, or an ability to interact withcomponents of a solution applied to the substrate material. Plasma-basedsurface modification may alter the characteristics of a surface of thesubstrate material by breaking chemical bonds at the material surface.Broken chemical bonds at a material surface may react with one or moreplasma species. Thus, the chemical structure of the surface may bemodified and the surface may be functionalized. After functionalization,a surface of a material may have a different characteristic (such as adegree of hydrophobicity hydrophilicity) than before functionalization.Further, a functionalized surface may be able to bind to chemicalcompounds or biomaterials used for chemical testing, in vitrodiagnostics, or point of care diagnostics.

In an exemplary embodiment, a substrate material may include a top layerof poly-methyl-methacrylate (PMMA). PMMA may be modified orfunctionalized by exposure of the PMMA surface to plasma containingoxygen atoms. The plasma may break surface molecular bonds, and oxygenatoms from the plasma may react with the PMMA substrate material withoutdegrading the bulk of the PMMA substrate material. Thus, a number ofcarbon-oxygen bonds, including both C—O single bonds and C═O doublebonds, may be greater on functionalized PMMA surface after plasmaexposure than on the original PMMA surface prior to plasma exposure. Newfunctional groups, such as the C—O single bonds and the C═O double bondsdescribed above, may be involved in further functionalization steps tobind other compounds to a substrate material surface for analyticaltesting purposes or to receive chemical treatment to make materials morebiocompatible. Surface modification or surface functionalization may berelevant to developing or manufacturing analytical testing devices,diagnostic probes, or medical devices.

Among the diagnostic probes and analytical devices that may be developedusing plasma processing are microfluidic devices that direct the flow ofsmall volumes of fluid through channels toward locations in themicrofluidic device that are configured to perform chemical, electrical,or optical tests on the fluid. Microfluidic device manufacturing may beinclude one or more masking steps. Masking may be performed on asubstrate surface for patterning purposes. Masking and functionalizationmay be performed on a substrate to induce interaction between thesubstrate surface (e.g., the unmasked portion) and a fluid analyte onthe surface. Masking may be performed to modify a behaviorcharacteristic of a fluid analyte (e.g., evaporation reduction bymodifying surface tension of the fluid). Masking processes associatedwith traditional methods of surface functionalization may be performedto protect masked portions of a substrate material fromsurface-modifying processes while exposed portions of the substratematerial surface may undergo functionalization. While masking of asurface may be advisable during manufacturing of a microfluidic device,processing conditions for removing a mask material may harm apreviously-functionalized area of a surface. For example, a surface maybe masked by applying a layer of photoresist to the material surface,followed by an exposure process and a developing process, wherein apattern is formed in the photoresist layer. Plasma may be applied to thesubstrate to functionalize the exposed portion of the substrate, whilethe masked portion of the substrate is protected by thephotoresist/However, removal of the photoresist layer, typicallyperformed by applying a solvent (such as acetone or alcohol) to thephotoresist may reduce a degree of functionalization of the exposedportion of the substrate. In some embodiments, compounds used to removephotoresist may also remove the functionalization of the materialsurface. Further, compounds that may remove photoresist or other maskingmaterials may be incompatible with biological materials applied to asurface, or with biological substrate materials. Organic materials orpolymeric materials may also be adversely affected upon exposure tomask-removing chemistries.

Traditional plasma-based surface modification methods may involve hightemperatures in plasmas and on surfaces of the substrate, may involvelarge currents, or may have high ion impact energies or particlevelocities. In some embodiments, biomaterials such as tissues,membranes, or enzymes, may not retain desirable characteristics uponexposure to conditions associated with traditional plasmas, includinghigh electron energy, high current, or high temperatures.

Substrate masking may also involve additional cost and manufacturingcomplexity to perform. For example, masking may involve additional stepsin order to clean substrates, apply mask materials, pattern maskmaterials, and remove mask materials after a chemical or plasma surfacemodification is performed. Increased cost may result from at least oneof additional time, additional materials, additional manufacturingequipment associated with masking, or additional cleaning steps duringmanufacturing. Further, additional handling and storage steps forsubstrates may increase facilities cost and provide opportunities forsubstrates to be damaged during a manufacturing process, loweringoverall yield of the devices being manufactured.

In an embodiment of the present disclosure, instead of masking asubstrate surface for patterning purposes, one may generate a plasmathat has spatial resolution determined by the spatial characteristics ofthe electron beams. In a non-limiting embodiment, a plurality ofdirectional electron beams with spatial separation may make a pattern ofmicro plasmas corresponding to the pattern of the directional electronbeams, retaining at least some of the spatial separation of the pattern.According to an embodiment, the pattern of micro plasmas may be modifiedduring operation of a plasma device by regulating a pattern of electronbeams that form the micro plasmas. During a surface functionalizationprocess, a pattern of electron beams/micro plasmas may be regulated tobypass areas of the substrate surface that may have already beenfunctionalized by a plasma device or some other process. Patterning asubstrate using an array of micro plasmas generated by a patterning headmay lead to increased throughput processed devices because theplasma-processing volume (the working volume) has a largercross-sectional area against a surface of a substrate than singleelectron-beam processing equipment.

It may be desirable to reduce cost of manufacturing objects withmodified surfaces or functionalized surfaces by directly making patternsof surface functionalization on a substrate, using a plasma device withspatial separation between electron beams (or, between micro plasmas). Adistribution of micro plasmas may involve gaps between individual microplasmas, or between groups of micro plasmas. Gaps in a distribution orpattern of micro plasmas may correspond to positions, between the microplasmas, where a surface may have undergone previous functionalization.Gaps in the distribution of micro plasmas may preserve previous surfacefunctionalization during a subsequent surface functionalization process.A distribution of micro plasmas may undergo changes according to aposition of the patterning head over a substrate being functionalized.The pattern may undergo changes according to a number of surfacefunctionalization steps that may already have been performed in an areaof a substrate surface.

Embodiments of an apparatus to perform spatially-selective nanoscalesurface functionalization may include: an electron source having a gridor an array of beam sources, a gas supply system to regulate a chemicalcomposition of a working volume where a plasma can form, and a movementsystem to regulate a position and alignment of a substrate with regardto the patterning head of a plasma device. Some embodiments of theapparatus may also include a gas delivery system wherein a gas orliquid, or combinations thereof, may be added to a working volume inorder to modify the gas composition (and, therefore, a type of surfacefunctionalization.

Spatial resolution of micro plasmas may decrease the number ofmanufacturing steps involved in generating surface-modified orsurface-functionalized devices, increasing device manufacturingthroughput. Spatial resolution of micro plasmas may enable plasmamodification and functionalization at pressures above the range ofpreviously available plasma modification devices (e.g., at or aroundatmospheric, or 1 bar of pressure. For example, during a manufacturingprocess, a plasma-based surface modification device may pattern asubstrate by positioning a patterning head of the plasma device inproximity to a substrate and performing plasma-based servicemodification at atmospheric pressure, or at pressures ranging from about0.5 to 2 atmosphere (atm), without damage to the substrate during amodification process. The ability to operate a patterning head of aplasma device at approximately atmospheric pressure may greatly reducemanufacturing time because a substrate may be modified without placingthe substrate in a pressure chamber having reduced or elevatedpressures, reducing the need for chamber palm down or chamber purgingtimes.

In some embodiments, a patterning device may be operated with anadjustable gas mixture and or plasma composition, at approximatelyatmospheric pressure, by directing a flow of gas or a flow of atomizedor evaporated liquid, into a working volume between a portion of thepatterning device where the plasma is generated and an area of asubstrate where service modification is being performed. By adjustingthe chemical composition of the gaseous mixture before plasma generationand during plasma generation, the chemistry of a substrate surface maybe regulated to generate predetermined distributions of surfacefunctionalization according to the chemical composition of the plasma.

A patterning head having spatial control of the plasma above a surfaceduring a modification process may involve generating a plurality ofmicro-plasmas arranged in an array between the patterning head and thesurface of the substrate. The micro-plasmas may remain discrete, or maymerge to form larger plasmas. The working volume between a patterninghead and a substrate being modified during a manufacturing process maycontain a plurality of volumes, each of which may contain anindividually adjustable micro-plasma. Thus, each volume may have a microplasma that is turned off or turned on independent of other volumes withother micro-plasmas (e.g., the micro plasmas, or the array loci at whichmicro plasmas may be generated, may be individually addressable). Thus,spatial control of the plasma in the working volume may afford greatermanufacturing flexibility during modification of the process tofunctionalized only a desired and controllable portion of a substratewhile leaving other options of the substrate unmodified by the presentplasma modification process.

A patterning head may include an electron source that generatesdirectional beams of electrons. An electron source may include one ormore emission structures that generate electrons that can form directedbeams. Emission structures may include thermionic emission structures,field-emission (FE) structures, or pyroelectric (PE) structures.Thermionic emission structures may generate beams of electrons after thestructures are heated in the present of a strong external electricalfield that can accelerated the emitted electrons from the thermionicemission structures toward a substrate surface outside a patterninghead. Field emission structures may involve electron emission in thepresence of a strong electrical field (stronger than for thermionicemission structures), but at lower temperatures for the emissionstructures (as compared to thermionic emission structures). Pyroelectric(PE) structures may generate electron beams following rapid thermalcycling of PE structures with large thermal gradients, in the presenceof an accelerating voltage that is significantly smaller than theaccelerating voltage for either thermionic emission or FE emission.

Electron emission structures may occur singly, or in clusters, at alocation in an electron source. In an embodiment, electron emissionstructures may occur in arrays, where each locus of the array, whetherpopulated by a single electron emission structure or by a cluster ofelectron emission structures, may be individually addressable (e.g.,each locus may be regulated independent of each other locus of thearray). Thermionic electron emission structures may consume more energyto generate an electron beam than do FE or PE electron emissionstructures because of the elevated operational temperatures. FE electronemission may use an intermediate amount of energy, resulting from thestrong electrical fields applied within the patterning head, to triggerelectron beam formation. PE electron emission may use less energy thaneither thermionic electron emission or FE electron emission becauseelectrons collect on emission structures and may be accelerated withlower voltages than for thermionic emission or FE emission. FE and PEnanostructures may be more compatible with organic materials, polymericmaterials, or biomaterials than traditional methods of producing plasmato modify a surface.

Electron sources with field emission nanostructures tend to operate atmuch lower temperatures than either thermionic or DBD plasma sources, tothe extent that the process is dubbed “cold emission”. Electron emissionstructures, as disclosed herein, may generate directional electron beamswithout use of magnetic lenses to focus and direct the beam of electronsonto a substrate. A patterning head without magnetic lenses may beconsiderably smaller a plasma device that uses magnetic lenses to focusa beam. By omitting magnetic lenses from a structure containing anelectron source, the manufacturing cost of the plasma device may beconsiderably reduced. Individually addressable electron emissionstructures may result in formation of micro plasmas in a working volumeoutside of a patterning head of a plasma device when a directed electronbeams strikes a primed atmosphere. Directed beams of electrons may beaccelerated by an electron accelerating structure into the primedatmosphere with an energy associated with the potential differencebetween the electron emission structure and the electron acceleratingstructure. Directed beams of electrons may be focused by optional beamcontrol apertures that expand or compress a distribution of the directedbeams around a center point of a path between the electron source andthe substrate

FIG. 1 depicts a cross-sectional diagram of an embodiment of a spatiallyselective surface functionalization device, or a plasma device, 100.While the embodiment described herein may be representative of otherembodiments, not all features of the plasma device 100 may be present ineach other embodiment of the present disclosure that is describedherein. Conversely, other embodiments of a plasma device may haveadditional elements that are not described in the embodiment of FIG. 1,but may still contain aspects of the present disclosure sufficient tofall within the scope of said disclosure.

Plasma device 100 may contain a movement system (or stage) 102, on whicha substrate 104 may be situated for surface functionalization, locatedbelow a patterning head 106. During operation of plasma device 100,patterning head 106 may generate plasma 108 in a working volume 110between a window 112 of the patterning head 106 (through which adirected beam of electrons 114 may pass to trigger plasma formation) andthe substrate 104. During operation of plasma device 100, the patterninghead 106 may be situated a working distance 115 above a top surface ofsubstrate 104. Working distance may range from about 10-micron to a 1millimeter, according to embodiments of the present disclosure. In someembodiments, a working distance may increase or decrease during surfacefunctionalization of the substrate according to a plasma density withinthe working volume, according to the size of the pattern being formed onthe substrate, or according to a composition of the plasma duringsurface functionalization.

The patterning head 106 of plasma device 100 may include an aligner 116configured to adjust pitch (parallelism between patterning head andsubstrate) and orientation (provides rotational control of the substratebeneath the patterning head) of the patterning head 106 with regard tothe movement system 102 and a substrate 104 located thereon. Movementsystem 102 may be configured to adjust a lateral position of thepatterning head 106 and any substrate thereon with regard to thepatterning head 106. Movement system 104 may be configured to movecontinuously, or to move incrementally, below the patterning head 106.Incremental movement of the substrate below the patterning head may bebeneficial for functionalizing discrete blocks of substrate material ona top surface of the substrate, where the blocks or regions of the topsurface do not contain structures that extend continuously betweenadjoining blocks. Continuous movement of the movement system, and thesubstrate material, below the patterning head may be beneficial forfunctionalizing, on a top surface of the substrate, patterns that havecontinuous extensions across borders of adjoining blocks or regions of asubstrate top surface. According to some embodiments, functionalizing asubstrate material top surface may involve a process of gradualmodification of a distribution of micro plasmas in the working volumebetween the patterning head and the substrate. According to someembodiments, functionalizing a substrate material top surface mayinvolve forming a first distribution of micro plasmas within a workingvolume, extinguishing the micro plasmas, adjusting a position of thepatterning head over the substrate, and re-ignition of a distribution ofmicro plasmas at a second position of the patterning head at a secondposition above the substrate.

Micro plasmas may be formed in working volume 110 between the patterninghead 106 and the substrate 104 by a directed beam of electrons 114emitted by an electron source 118 located in a cavity 120 of an electronsource housing 122. A membrane 124 may be located between electronsource 118 and the working volume 110. An electron acceleratingstructure (or, accelerating structure) 126 may be located in a planebelow a bottom surface of the electron source 118. Having the electronsource 118 positioned “above” the electron accelerating structure 126may allow the electrons generated by the electron source 118 to beaccelerated by a positive voltage on the electron accelerating structure126 such that the electrons achieve a desired electron energy (measuredin electron volts, or eV) as the electrons pass through the membrane 124and the window 112 before striking atoms and molecules in the workingvolume to trigger plasma formation.

According to embodiments, electron source 118 may have a plurality ofindividually addressable electron emission structures located therein,each capable of generating a beam of electrons that may be acceleratedtoward the membrane 124 and window 112 into working volume 110.

Electron accelerating structure 126, electron source 118, aligner 116,and movement system 102 may receive electrical power from a power supply128 over electrical connections 130. Electron accelerating structure 126may receive an electrical voltage configured to attract electrons fromelectron source 118 out of electron source 118 and toward working volume110 and substrate 104. According to some embodiments, an electronaccelerating structure may operate with an electrical voltage less thanan electrical voltage ranging from about 1 kV to about 50 kV, such thatelectrons exiting an electron source may have an electron energy rangingfrom about 1 keV to about 50 keV. An electron accelerating structure mayhave a coating of thin films to prevent discharging between the electronaccelerating structure and components of the plasma device, includingthe electron source and electron emission structures located therein. Anelectron accelerating structure may be made of one or more metals, orlayers of metals, or alloys of multiple metals, such as copper,aluminum, tungsten, titanium, or platinum.

A plasma device may have a control element 132 (or a pattern managementsystem) configured to handle information regarding the relativepositions of movement system 102, substrate 104, and aligner 116, aswell as regulating information about the pattern being functionalized ona top surface of the substrate and the formation of the plasma, or microplasmas, in the working volume 110 during surface modification and/orfunctionalization. Control element 132 may include a communication bus134, a pattern repository 136, a pattern buffer 138, a emissionstructure activation element 140, and an instruction generator 142.Control element 132, or the subcomponents of control element 123,including emission structure activation element 140, may be programmableto convert a pattern, or a portion of a pattern, into a dynamicallyupdated pattern of electron beams and micro plasmas during patterninghead operation. Communication bus 134 may interconnect patternrepository 136, pattern buffer 138, emission structure activationelement 140, and instruction generator 142 to each other and to aligner116, electron source 118, and to movement system 102 in order tofacilitate regulation of substrate position, alignment, or orientation,and to regulate formation, adjustment, or extinguishing of plasmas ormicro plasmas below patterning head 106 in working volume 110.

Pattern repository 136 may be configured to receive, over a dataconnection or input/output port, information regarding a pattern to beformed during a surface functionalization process on a top surface ofsubstrate 104. The pattern may include information regarding theboundaries and shapes of areas or regions on a substrate top surface,the type of functionalization that is intended for each area or regionon the substrate top surface, and the processing conditions (includingplasma composition, electron energy, plasma density, working distance,exposure time, and micro plasma pattern regulation parameters) that canproduce a region of surface functionalization on the substrate topsurface.

Pattern buffer 138 may include a storage medium such as DRAM (dynamicrandom access memory), a hard disk drive, a solid state drive, or someother form of volatile or non-volatile storage medium where informationregarding a portion of one or more patterns stored in the patternrepository 136 may be transferred and manipulated in order to perform asurface functionalization process. Information regarding the portion ofone or more patterns in a pattern repository may be transferred from apattern repository to a pattern buffer for manipulation andcommunication to an instruction generator 142. Further, informationregarding the completion status of surface functionalization of asubstrate, or a portion thereof, may be stored in a pattern buffer andcommunicated back to the pattern repository in order to facilitatetransfer from the pattern repository to the pattern buffer of anotherportion of one or more patterns.

Instruction generator 142 may be connected to pattern buffer 138 overcommunication bus 134 in order to receive a portion of the informationregarding a portion of one or more patterns stored in the patternbuffer. Instruction generator 142 may be programmable, configured toanalyze the information and to generate, based on the informationregarding the pattern, and on previous, present, or upcoming processingconditions for surface functionalization, on the material of thesubstrate 104, on the progress in functionalizing a surface of thesubstrate with the pattern, and on a position of the substrate withregard to the patterning head 106, instructions for performing currentor upcoming surface functionalization steps. According to an embodiment,the instructions may include instructions on a rate of motion of thesubstrate below the patterning head, instructions on modifying a workingdistance between the patterning head and the substrate, instructionsabout modifying a composition of the gas mixture in the working volume,instructions about retaining a distribution of micro plasmas within theworking volume, or about modifying a distribution of micro plasmas,instructions about modifying an accelerating structure voltage to modifyelectron energy within the working distance, or instructions about atype of motion of the substrate with respect to the patterning head(i.e., continuous or step-wise motion of the substrate, and instructionsregarding modifying a degree of focus (or, of a degree to which adistribution pattern of micro plasmas is compressed before the patternimpinges on the top surface of the substrate.

A distribution of micro plasmas generated by the patterning device maybe modified by instructions from the instruction generator 142 to ananostructure activation element 140 for regulation of the pattern ofelectron emission structures that emit electron beams in an array ofelectron emission structures of an electron source. An instruction to aemission structure activation element may include further instructionsregarding the activation or deactivation of individual electron emissionstructures (or, loci having clusters of emission structure structures):when an instruction is performed by the emission structure activationelement, some emission structures may become activated, some may becomedeactivated, some may remain activated, and some may remain deactivated,according to the pattern of functionalization being performed at thetime of the instruction performance, and according to a position of thesubstrate below the patterning head.

Patterning head 106 may further include one or more nozzles (or micronozzles, or orifices) 144, connected to one or more reservoirs 146 witha flow regulator 148, configured to supply a fluid mixture to theworking volume 110 between patterning head 106 and substrate 104.According to an embodiment, a supply of fluid (a gas or a liquid) to theworking volume during surface modification may adjust the chemicalcomposition of the substrate top surface during the surface modificationprocess. According to an embodiment, a fluid mixture may include one ormore gaseous species, or may include a volatilized (or aerosolized)liquid that, upon evaporation, provides a gaseous component for the gasmixture. Chemical species that may be used for surface functionalizationinclude compounds for increasing a concentration of surface oxygen on asubstrate surface, compounds for increasing a concentration of a halogenon a substrate surface, and compounds for increasing a concentration ofnitrogen on a substrate surface. Chemical species that functionalize asurface may be radicals or nonradicals. Chemical species that maypromote functionalization of a surface with halogen atoms, includingchlorine or bromine, may include atomic chlorine or atomic bromine, ornon-radical species such as: hypochlorous acid (HOCl), nitryl chloride(NO₂Cl), chloramines, chlorine gas (Cl₂), bromine chloride (BrCl),chlorine dioxide (ClO₂), hypobromous acid (HOBr), or bromine gas (Br₂).Chemical species related to addition of oxygen to a substrate surfacemay include radicals or non-radical species, such as: superoxide (O₂.⁻),hydroxyl radicals (HO.), hydroperoxyl radical (HO₂.), carbonate (CO₃.⁻),peroxyl radicals (RO₂.), where R is a carbon or other atom, and alkolxylradicals (RO.), where R is a carbon or other atom, as well as nonradicalspecies such as hydrogen peroxide, hypobromous acid (HOBr), hypochlorousacid (HOCl), ozone (O₃), organic peroxides (ROOH), where R═C,poroxynitrite (ONOO⁻), or peroxynitrous acid (ONOOH). Chemical speciesrelated to addition of nitrogen to a substrate surface may includespecies such as nitric oxide NO., nitrogen dioxide NO₂., nitrate radical(NO₃.), nitrous acid (HNO₂), dinitrogen tetroxide (N₂O₄), dinitrogentrioxide (N₂O₃), peroxynitrite (ONOO⁻), peroxynitrous acid (ONOOH), ornitryl chloride (NO₂Cl).

Nozzles 144 may have a pressure that is greater than the pressure ofambient atmosphere in the working volume. In some embodiments, nozzlesmay have a pressure that is lower than the pressure of ambientatmosphere. Nozzle pressures below ambient pressure may allow evacuationor flushing of the working volume, removing spent or reacted gases andbyproducts from the working while some nozzles with pressures aboveambient pressure supply new fluids (e.g., gases or aerosolized liquids)for surface functionalization. By adjusting the pressures of thenozzles, plasma in the working volume may be reshaped, or resized, inorder to adjust the pattern of surface functionalization duringsubstrate processing. Nozzles may be arranged along opposite sides ofthe patterning head, in some embodiments. In an embodiment, nozzles maybe arranged around a perimeter of the patterning head. Nozzle pressuresmay be regulated independently, or in groups, according to someembodiments of the present disclosure. Regulating nozzles in groups mayreduce a number of fluid handling components (e.g., flow regulators,reservoirs, supply lines, etc. . . . ).

FIG. 2 depicts a cross-sectional view of an embodiment of a patterninghead 200 having field emission structures. The cross-sectional viewincludes a depiction of a path traveled by directed beams of electrons202 outward from a chip 203 of the electron source 204. Chip 203includes at least one field emission structures 206, the at least onefield emission structure being oriented downward toward an electronaccelerating structure 208, a membrane 210, and a working volume 210.The directed beams of electrons 202 may intersect a primed gas mixture216 in working volume 210, composed at least partially by a gas 214emitted by one or more nozzles 212 oriented toward working volume 210.Plasma 218 may be formed by the intersection of directed beams ofelectrons 202 with primed mixture 216 in working volume 210.

Electron source 204 may be a sealed structure with the field emissionstructures at an electrical potential less than the electrical potentialof an electron accelerating structure 208. Electron source 204 may, uponapplication of a positive electrical potential to the electronacceleration structure 208, and upon application of a negativeelectrical potential to field emission structures, cause directedelectrons to travel toward a substrate for plasma formation. Uponpassage of directed electrons through the membrane 210 and into theworking volume, one or more micro plasmas may be formed in a workingvolume. The working volume may be a controlled region that can undergospatial adjustment (as by, for example, modifying a working distancebetween a substrate and the patterning head), by regulating the gastemperature, by regulating the gas composition, or by adjusting a flowrate of the primed mixture in the working volume.

In some embodiments, an electron mask (not shown) may be positioned inthe path of the directed electron beams in order to absorb some of theelectrons while passing other of the electrons, forming a patternedplasma in the working volume. One advantage to using individuallycontrollable field emission structures of an electron source is theability to dynamically reconfigure a distribution or pattern of microplasmas within the working volume without removing or replacing aphysical electron mask of the patterning head.

According to some embodiments, the chip 203 may be a substrate materialwith an interleaved conductive network that makes contact with the FEnanostructures of the electron source. The chip substrate material maybe made of one or more of silicon, silicon dioxide, quartz, or someother combination of semiconducting and dielectric materials thatprovide insulation between elements of the interleaved conductivenetwork that provides a conductive path between the field emissionstructure and the power source of the patterning device.

Field emission structures 206 may include silicon nanowires, siliconcarbide nanowires, carbon fiber nanowires, carbon nanotubes, or someother conductive material. Field emission structures may be depositedonto conductive pad areas of the chip. In some embodiments, fieldemission structures may be grown in situ on conductive pad areas of thechip. According to an embodiment, field emission structures may beformed by seeded growth, self-organized assembly, or adhesion ofemission structures to a conductive pad of the electron source. Fieldemission structures may have distal ends extending toward the electronaccelerating structure of an electron source. Upon exposure of the fieldemission structures to an attracting (positive) voltage at the electronaccelerating source, individual field emission structures, or loci offield emission structures in an array of conductive pad areas of thechip, may, when at a negative potential individually (or, as a groupwhen a plurality of field emission structures are located at a singlelocus of the array) emit electrons. In an embodiment, a voltage appliedto at least one locus in an array of field emission structures, or to atleast one field emission structure, may be between about −1 kV and about−10 kV in order to promote formation of a beam of directed electronsduring surface functionalization and/or surface modification processes.Electron emission from the field emission structures may be modifieddynamically by instructions supplied by the instruction generator to thefield emission structure activation element of the control element of apatterning device.

Electron accelerating structure 208 may be a mesh or a ring structureheld at a positive voltage with respect to the field emission structures206 of the electron source 202. An electron accelerating structure maybe located within the electron source 202 in proximity to the fieldemission structures such that the electrical field strength at the fieldemission structures is sufficient to allow electrons to escape from thefield emission structures without elevated temperature (as would be thecase with thermionic emission electron sources) or significantly largevoltage differentials (as would be the case with a DBD electronsources). According to an embodiment, an electron accelerating structuremay be made of a metal, such as tungsten, copper, aluminum, titanium,platinum, or another metal suitable for shaping into a mesh or ringstructure within the electron source. In some embodiments, the metal maybe corrosion resistant to withstand impacts of directed electron beamsand to avoid oxidation/reduction reactions of the metal with any gaspresent within the patterning head. Electron accelerating structure 208may be used to extract electrons from the electron source, accelerateelectrons toward the substrate, focus electrons into a smaller area thanthe area of the array of FE nanostructures, or scan the directed beamsof electrons across a region of a membrane or across the working volumeduring operation of the plasma device.

Membrane 210 may include a first membrane face 210A and a secondmembrane face 210B, with the first membrane face closer to the FEnanostructures and the second membrane face closer to the substrate. Inan embodiment, first membrane face may be a conducting layer and secondmembrane face may be a non-conducting layer. In an embodiment, firstmembrane face 210A may be made of a conducting material, or alloys ofconducting metals, such as copper, aluminum, tungsten, titanium, orplatinum. In an embodiment, second membrane face 210B may be made of anon-conducting material such as silicon dioxide or silicon nitride oranother insulting material. The combination of the emission structures206 and electrodes 210A and 210B may be considered a triode arrangement.According to an embodiment, one of the membrane faces may be formed bydeposition, either by sputtering, chemical vapor deposition, epitaxialgrowth, or electrochemical deposition, of one of the materials amembrane face on a thicker layer of material of the other membrane face.For example, a metallic layer may be formed by sputtering orelectroplating of a metal such as tungsten, on a thicker layer ofsilicon nitride, to form a tungsten/silicon nitride membrane. Othercombinations of conducting and non-conducting membrane combinations maybe readily apparent to practitioners of the art using common depositionand film-growth techniques.

Electrons can penetrate through a thin membrane if their kinetic energyis much larger than the energy lost in the membrane material bycollisional scattering. Typically, these membrane are made of conductivemanufacturable material including, but not limited to, metals such asTi, Cu, W, or conductive organic materials such as carbon, graphene,fullerene-like materials, or carbon nanotubes. A combination of electronenergy ranges and membrane ranges are generally 5,000V to 20,000V and 1nm to 100 nm, respectively. In some manifestations, a thin dielectricmaterial is added to assist in the fabrication of the conductivemembrane and act as backing to the membrane, the thickness of thedielectric satisfies the condition for small relative loss of theelectron beam energy in the dielectric, typically this dielectric is SiNor similar material and is less than 300 nm thick.

As described previously, directed electron beams 202 emitted from fieldemission structures 206 may be directed downward into a working volume210 to generate a plasma comprising ionized gaseous species. Compositionof the plasma may be modified by modifying, during surface modification,a chemical composition of the primed gas mixture in the working volume210. One benefit of a lower voltage electron source such as a sealedelectron source having a chip with field emission structures may be thatthe primed gas mixture may be a static, or stationary, gas mixture. Theplasma, or micro plasmas, formed in the working volume may be formedwith little or no arcing or pressure fluctuations because of the lowerelectron energies for field emission electron sources, as compared toother electron sources such as thermionic emission electron sources.Further, because plasmas may be formed with static gas mixtures presentin the working volume, with gas flow rates ranging from about 1 ml/minto about 100 ml/min.

FIG. 8 depicts a plasma device 800 having an electron emission structurearray 806 in an electron source substrate 804. In some embodiments, theelectron source substrate may be a chip comprising semiconductormaterials with nanostructures located thereon as depicted in FIG. 3,below. Electron emission structure array 806 may include diodestructures configured to generate electron beams 802. Electron sourcesubstrate 804 and electron emission structure array 806, as well aselectron accelerating structure 808, may be located within a sealedenclosure 801, configured to operate at a first pressure in the sealedenclosure that is lower than an external pressure outside the sealedenclosure. Electron accelerating structure 808 may be a conductivematerial such as a mesh or thick conductive membrane. Some embodimentsof electron accelerating structures may include materials that aresimple to manufacture into mesh or ring-like structures, includingtitanium, copper, tungsten, graphene, etc. . . . . Electron acceleratingstructure 808 may extract electrons from nanostructures in the electronemission structure array 806 by holding, during operation of the plasmadevice, a positive voltage, while the nanostructure of the electronemission structure array 806 may hold a negative voltage. Electronaccelerating structure may also serve to accelerate extracted or emittedelectrons from the nanostructures along a path toward sealing membrane811 and working volume 810 (outside the sealed enclosure 801).

Electron accelerating structure 808 may be kept at a potential that isless negative than the substrate 804 and the electron emission structure802 combined. As a non-limiting example, the substrate 804 can be heldat potential between about −1 kV and about −10 kiloVolt (kV) withelectron accelerating structure 808 grounded (0 V). The final electronenergy of electrons in electron beams 802, as they exit sealed enclosure801, may be a function of the total potential difference between theelectron accelerating structure 808 and electron source substrate 804.

The distance between the electron source substrate 804 and the electronaccelerating structure 808 may be significantly smaller than a lateralmeasurement (length, width) of the electron source substrate 804. Aratio of about 5:1 (lateral measurement to separating distance) may bedesirable in order to maintain a uniform electric field and to promoteformation of parallel beams of electrons upon electron emission fromnanostructures of electron source substrate 804. The ratio may be asmuch as 10:1, while still maintaining uniform electric fields in theplasma device. Ratios smaller than about 5:1 may lead to significantelectric field distortions. As with patterning head 200, sealedenclosure 801 may have an interior pressure smaller than the exteriorpressure. A sealing membrane 811 or, in some embodiments, a hardaperture (not shown) capable of active differential pumping, may beused. A hard aperture may further serve to confine the electron beams802 in a lateral dimension. Working volume 810, nozzles 812, gases 814,and primed mixture 816, the plasma formation 818 are similar to thedescription of corresponding elements of FIG. 2, wherein the numeralsare incremented by 600.

FIG. 9 depicts an embodiment of a plasma device 900 having a pluralityof pyroelectric (PE) electron emission structures (pyroelectriccrystals) 904 located within sealed enclosure 901. Pyroelectric electronemission structures 904 may be situated at a distal end of individuallyaddressable thermal elements 906, the distal end being closer to theelectron accelerating structure 908 than to a wall of the sealedenclosure 901. Pyroelectric electron emission structures may be made ofmaterials including, but not limited to, lithium niobate (LiNbO₃),lithium tantalate (LiTaO₃), or barium titanate (BaTiO₃).

Individually addressable thermal elements 906 may be configured toundergo large amplitude, high gradient thermal changes to generate,within the pyroelectric nanostructures, a residual electrical charge onindividual pyroelectric nanostructures. Individually addressable thermalelements 906 may include one or more micro heating elements and one ormore micro cooling elements, configured to rapidly modulate atemperature of the individually addressable thermal elements, and thepyroelectric nanostructures located thereon, to induce electronaccumulation on the PE electron emission structures. A number of microheating element sand micro cooling elements in an individuallyaddressable thermal element may be determined according to the chemicalstructure of the PE electron emission structures located thereon, andthe individual electron accumulation characteristics of the PE electronemission structure material.

Electrical charges accumulated on PE electron emission structures may beinduced to leave the PE electron emission structures and travel throughthe sealed enclosure in directed electron beams. An electronaccelerating structure 904 may trigger departure of electrons from PEelectron emission structures, and may accelerate the electrons toward asubstrate in order to cause plasma formation above a substrate surface.PE electron emission structures may be held at a negative voltage ofbetween about −2 kV and about −10 kV, and an electron acceleratingstructure may be held at a positive voltage of about +10 kV, in order topromote electron beam formation and to regulate electron energy in theplasma formed in working volume 910. Pyroelectric emission may occur atpressures within the sealed enclosure 901 of about 1 Torr, althoughother pressures may be employed according to voltage configurations ofthe plasma device and the identity of the gas within the sealedenclosure. Pyroelectric emission may occur with voltages that aresignificantly lower than thermionic emission or DBD electron sources,reducing a cost of manufacturing of materials using a plasma device asdisclosed herein.

Individually addressable thermal elements, and pyroelectric electronemission structures 904 located thereon, may be arranged in an arrayhaving a plurality of loci, each locus being individually addressable totrigger electron emission from one locus independent of electronemission status at a second locus within the array. Elements of FIG. 9not mentioned above resemble the corresponding elements of FIG. 2,having identifying numbers incremented by 700.

FIG. 3 depicts a cross-sectional view of an embodiment of a chip 300 ofan electron source. Chip 300 comprises a substrate 302 having aplurality of electrical connections (not shown) extending through thesubstrate 302 and connecting to a nanostructure activation element in acontroller element (or, a pattern management system) of a plasma deviceas described previously. Electrical connections may include a pluralityof contacts 306 or pads having a contact top surface 308 that isexposed. Spatial selectivity of the patterning device may relate to thepitch between contacts 306 of an electron source, and to the ability ofa nanostructure activation element to, upon receiving an instructionfrom an instruction generator of a controller element (see FIG. 2,above), modify the activation status of individual FE nanostructures(or, of FE nanostructures at a single locus in an array of contactshaving FE nanostructures on the top surfaces of the contacts.

According to some embodiments, a remainder of a contact (the portionother than the contact top surface) may be surrounded by substratematerial or other materials of the chip. The substrate 302 may have asubstrate top surface 308 that is covered by layers of material 312 and314 that insulate the contacts 306 and electrical connections from theelectrical field of an electron accelerating structure of the electronsource. In an embodiment, a contact top surface may be approximatelycoplanar with a substrate top surface. According to an embodiment, acontact top surface may be recessed below a substrate top surface. In anembodiment, a contact top surface may extend above a substrate topsurface.

Contact top surface 308 may be covered by one or more electron emissionstructures 316 from which a directed beam of electrons may be drawn byan electron accelerating structure of an electron source. Electronemission structures 316 may include nano rods, nanowires, carbonnanotubes, fullerene-like structures, tunneling cold field emittercathodes, or diode structures. Electron emission structures may be madefrom materials that include silicon, silicon carbide, carbon nanotubes,fullerenes, or pyroelectric materials. The electron emission structurearray in chip 300 may have a low impedance in order to facilitateelectron emission from the chip toward the electron acceleratingstructure. Impedance may be low enough that thermal loading is reducedand thermal damage to a chip or nanostructures thereon is reduced. Insome embodiments, the activation voltage for field emission fromelectron emission structures may be less than or equal to about 1 keV.Electron emission structures as described herein may reduce powerconsumption of a patterning head, as described above, to wattages belowabout 5 Watts. In some embodiments, power consumption may be reduced tobelow 1 Watt of power.

Electron emission structures 316 may be located below a chip top surface318 within chip openings 320. A working distance between chip topsurface 318 and a substrate surface during surface functionalization mayrange from 0 mm to about 1 mm, or more, while plasma modifies orfunctionalizes a substrate surface.

FIG. 4 depicts a cross-sectional analysis of an embodiment of plasmadevice 400. Plasma device 400 is shown, separated from a substrate 402by a working distance 404, during a surface functionalization process. Aplasma 406 may be formed in a working volume 408 upon ignition of theplasma by a directed beam of electrons 410 in a gas delivered to theworking volume 408 by a gas supply nozzle 412. Directed beam ofelectrons 410 may be emitted by an electron emission structure 416, uponformation of a large positive electrical voltage by an electronaccelerating structure 414, in proximity to electron emission structure416. Directed beam of electrons 410 may be drawn from the electronemission structure 416 by the electron accelerating structure 414,through a control ring (or control mesh) 418 and through a membraneand/or window 418.

A dimension of the plasma 406 may be regulated by beam defining aperture420, configured to electromagnetically compress or expand the directedbeam of electrons 410 during passage through membrane and/or window 418and formation of plasma 406. In some embodiments, a dimension of theplasma may be increased by the beam defining aperture to expose a largerdimension of substrate to plasma during surface functionalization. In anembodiment, a dimension of a plasma may be reduced in order to generatesmaller features and to restrict plasma-induced damage, or thelikelihood thereof, upon sequential surface functionalization steps on asubstrate top surface.

Plasma device 400 may have an electron scanning element 422 configuredto steer directed beam of electrons 410 across a top surface ofsubstrate 402 during surface functionalization. By regulating thestrength of an electromagnetic field of beam defining aperture 420, aposition of substrate 402, and a magnitude of electromagnetic fields ofelectron scanning element, an electron beam (or beams, according to anumber of electron emission structures in plasma device 400), may scribeplasma across a top surface of substrate 402 with spatial separationfrom already-functionalized regions of the top surface of substrate 402.According to a pitch between electron emission structures of the plasmadevice, and according to the magnitude of the beam definition field,inter alia, an array of directed electron beams may be “compressed” intoa distribution of directed electron beams having a separation betweenadjacent directed electron beams measured in units of micrometers ornanometers. A pitch between individual loci for electron emissionstructures may range from about 10 nm to about 1 mm, and a pitch betweenloci in an array of nanostructure clusters on a surface of an electronsource substrate may range from about 100 nm to about 1000 micrometers.A pitch of directed electron beams may range from about 250 nanometers(nm) to about 1 millimeter (mm) according to an embodiment. According toan embodiment, a second beam defining aperture (not shown) may be usedto contain a plasma (or, a plurality of micro plasmas) formed in aworking volume 408 between plasma device 400 and a substrate 402.

An electron emission structure 416 (or, an array of electron emissionstructures) may be formed on a low impedance substrate 424 of plasmadevice 400. In some embodiments, low impedance substrate may be a chipsuch as chip 203 of FIG. 3, described above. Low impedance substrate 424may be located within an electron source housing 426. An electricalconnection 430 may be connected to low impedance substrate 424, andconsequently to the electron emission structure 416 (or, the array ofelectron emission structures) thereon as a source of electrons for theelectron beam.

Electron source housing 426 may be under vacuum in an embodiment,Electron source housing 426 may be at a pressure less than ambientatmospheric pressure. Electron source housing 426 may have a gaseouscomposition that is different from the gaseous composition of ambientatmosphere outside of plasma device 400. Electron source housing 426 mayhave a gaseous composition that is different from the gaseouscomposition of the working volume between the patterning head and asubstrate. A pressure of within plasma device 400 may be reduced belowthe ambient outer pressure by withdrawal of gas from an interior ofplasma device 400 through a vacuum port 428.

FIG. 5A depicts a top-down view of part of a pattern offunctionalization of a microfluidic device 500. Microfluidic device 500may have a top surface 502 divided into a first region 504 and a secondregion 506. First region 504 and second region 506 may have a sameperimeter shape and a same-sized area within the perimeters thereof, andadjoin each other along one side. First region 504 and second regionhave different functionalization patterns located within the regionperimeters. Description of the process of functionalizing the regions504 and 506 may be illustrative of the performance of micro plasmafunctionalization in general on substrates. First region 504 and secondregion 506 contain a first set of areas 508, having a first type offunctionalization, and a second set of areas 510, having a second typeof functionalization thereon. First region and second region 506 may befunctionalized with the first and second sets of areas without a maskingprocess being performed to protect part of the top surface 502 fromdouble processing or destruction of a previously-functionalized areaduring a current functionalization step. Top surface 502 may alsocontain an area 502 that has a third type of functionalization thatdiffers from both the first type and second type of functionalizationfound in the first and second sets of areas. In an embodiment, the thirdtype of functionalization may be an original type of surfacefunctionalization present on a top surface of a substrate prior to anysurface functionalization by spatially selective plasma processing.

FIGS. 5B-5E depict patterns 520, 530, 540, and 550 ofspatially-selective surface functionalization that may be performed inorder to generate a surface functionalization pattern depicted inmicrofluidic device 500, described previously. For purposes ofconvenience in describing surface functionalization, the patternsdepicted herein share a common pattern perimeter 526. However, in manyembodiments, a pattern perimeter may have different dimensions during aprocess of performing surface functionalization, according to adimension of a pattern portion, and according to an ability of thepatterning head to modify a shape and dimension of a distribution ofelectron beams and/or micro plasmas during surface functionalization.FIG. 5B depicts first pattern 520, having an activated portion 524 and adeactivated portion 522 within a pattern perimeter 526. Activatedportion 524 includes two activated spaces within pattern perimeter 526.FIG. 7C depicts second pattern 530, having within pattern perimeter 526,deactivated space 532 and activated space 534. Deactivated portion 534includes a single activated space. FIG. 5D depicts, within patternperimeter 526, activated portion 544 and deactivated portion 542, andFIG. 5E depicts, within pattern perimeter 526, activated portion 554 anddeactivated portion 552. Activated portion 554 includes two activatedspaces.

In a representative, but non-limiting embodiment of a method of formingthe surface functionalization pattern depicted in microfluidic device500, the patterns depicted in FIGS. 5B-5E may be applied in any order.In an embodiment, functionalization patterns may be formed on asubstrate top surface sequentially in a single region (such as region504), before moving patterning head above second region 506 for a secondset of surface functionalization steps [e.g., patterns 520 and 540 maybe applied during functionalization of first region 504, prior tofunctionalization of second region 506 using patterns 530 and 550]. Inan embodiment, functionalization patterns may be formed in differentregions according to functionalization types, wherein, e.g. first set ofareas 508 may be functionalized before any areas of second set of areasare functionalized on top surface 502 [e.g., patterns 520 and 530 may beapplied to the first and second regions, completing functionalization offirst set of areas 508, before patterns 540 and 550 are applied to thefirst and second regions, completing functionalization of the second setof areas 510]. Because micro plasmas formed by the patterning head maybe regulated to remain separate within the working volume between apatterning head and a substrate top surface, spatial separation offunctionalized areas and micro plasmas may allow maskless plasmafunctionalization of top surface without harm to previouslyfunctionalized areas. Determination of an order of micro plasmapatterning of a substrate top surface may relate to a desired speed offunctionalization of a top surface, a complexity of a functionalizationpattern, a resolution of a micro plasma produced in the working volume,and other factors associated with compatible chemistry in the plasma,consumption of reactive species by the plasma during surfacefunctionalization, accuracy of positioning the patterning head withrespect to features on the substrate top surface, and a speed ofrefreshing or purging a working volume when changing from one type offunctionalization chemistry to a different type of surfacefunctionalization chemistry.

FIG. 6 depicts a flow diagram of an implementation of a method 600 ofgenerating a patterned array of micro-plasmas. In a first operation 602,at least one directional electron beam may be formed by applying apotential difference between an accelerating structure and an array ofelectron emission structures of an electron source. A number of electronbeams formed upon application of the potential difference to theaccelerating structure and the array of emission structures may be afunction of a number of individual emission structures, or loci of thearray of emission structures, in the electron source. A number andpattern of emission structures, or loci, may be adjusted duringoperation of a patterning head by an instruction received from a controlelement of a plasma device, where the control element stores a patternof surface functionalization, processes the pattern, sends informationregarding the pattern to an instruction generator to determine an orderof operations to form the pattern on a substrate surface, and regulatesthe distribution (or pattern) of micro plasmas that form a pattern byactivating or deactivating individual emission structures, or loci of anarray of emission structures, in the patterning device.

In an optional operation 604, the directed electron beam may be directedthrough a membrane having a first membrane face and a second membraneface toward a substrate. A membrane may be configured to permit creationof a pressure differential between an interior of a sealed enclosure andthe exterior of the sealed enclosure. A membrane may be selectivelypermeable to gases, or may have a pinhole located therein to allow somegas to enter the interior portion of a sealed enclosure while theinterior portion is being pumped to a reduced pressure. An interiorportion of a sealed enclosure may have a pressure as low as 10⁻⁹ Torrwhile an exterior portion (outside the sealed enclosure) may have apressure of about 760 Torr. The velocity, or energy, of the directedelectron beam, may be regulated by adjusting the potential differencebetween emission structures and the electron accelerating structure ofthe electron source. By regulating the electron beam energy, a plasmadevice may regulate plasma density, the species that are formed in themicro plasmas in the plasma, and (optionally) the impact velocity of theionized species against the substrate surface during surfacefunctionalization.

In an optional operation 606, the working volume between the patterningdevice and the substrate may be primed with a gas mixture supplied vianozzles of the patterning head to adjust the chemistry of the plasmaduring surface functionalization. The chemistry may be adjustedaccording to a type of functionalization desired in a particular part ofthe surface functionalization process. In an operation 608, at least onemicro plasma is ignited by directing the at least one directionalelectron beam

FIG. 7 depicts a flow diagram of an implementation of a method 700 formaking a spatially selective surface functionalization device, or plasmadevice. In an operation 702, an array of individually addressableelectron emission structures, or loci in an array of clusters ofelectron emission structures, may be formed on an electron sourcesubstrate. Electron emission structures may be thermionic emissionstructures, field emission (FE) nanostructures or pyroelectric (PE)nanostructures located on conductive pads of an electron sourcesubstrate, the conductive pads being connected to a power supply andconfigured to apply a negative voltage to the emission structures duringoperation of a plasma device.

In an operation 704, an electron accelerating structure may be formed ina patterning head in close proximity to an electron source substrate. Aratio of a lateral dimension of the electron accelerating structure anda distance between the electron accelerating structure and an electronsource substrate may range from between about 5:1 to about 10:1,although other, larger ratios, may be possible.

In an operation 706, electron emission structures of the electron sourcesubstrate, and the electron accelerating structure, may beinterconnected at a power supply configured to generate an electricalpotential between the electron source substrate and the electronaccelerating structure. In an embodiment, an electron source substratemay be held at a voltage between about −1 kV and about −10 kV, while anelectron accelerating structure may be held at a positive voltageranging between about +1 kV and about +10 kV.

In an operation 708, a membrane may be located in a wall of a sealedenclosure to allow passage of directed beams of electrons from thenanostructures of the electron source substrate to the working volumeoutside the sealed enclosure. A membrane may be a single film membrane,or may have bilayers configured to allow passage of electrons out of thesealed enclosure.

In an operation 710, a gas delivery system nozzle may be positioned todeliver a flow of gas into a working volume of a plasma device. Theworking volume may be located between the membrane and the surface of atarget substrate being functionalized by the plasma device. A workingvolume may have a gas flow delivery rate configured to refresh plasmareactant species during surface functionalization. A gas delivery systemmay include gaseous species and liquid species that may be aerosolizedor evaporated by a carrier gas in order to prime a gas mixture in theworking volume. In an operation 712, a controller element may beconnected to the plasma device to regulate activation and deactivationof the nanostructures during surface functionalization.

In various embodiments, the chip includes a substrate formed from one ormore of silicon, silicon dioxide, quartz, or silicon, preferablysilicon. The individually addressable electron emission structures ofthe emission structure array may be a combination of one or more of thefollowing: nano rods, nanowires made of a conductive or semiconductormaterial (such conductive or semiconductor materials including, but notlimited to silicon, silicon carbide, and carbon), as well as carbonnanotubes and fullerene-like structures, tunneling cold field emittercathodes, and pyroelectric material cathodes. Individually addressablenanostructures may be grown directly on a substrate material, or may bedeposited onto a substrate material, or regions of a substrate materialthat are electrically connected to a power supply for the electronsource of the patterning head.

In some embodiments, the techniques described herein may be used to forman analytical chip like that described in a U.S. patent applicationtitled SELF-FLOWING MICROFLUIDIC ANALYTICAL CHIP filed on the same dayas this patent filing, the contents of which are incorporated byreference. In some embodiments, the analytical chip may be analyzed witha pump-free microfluidic analytical system described in a U.S. patentapplication titled STAND ALONE MICROFLUIDIC ANALYTICAL CHIP DEVICE,filed on the same day as the present patent filing, the contents ofwhich are incorporated by reference.

What is claimed is:
 1. A device for spatially selective surfacefunctionalization, comprising: a pattern management system; a patterninghead; and a gas delivery system; wherein the patterning head isconfigured to generate a first distribution of micro plasmas against atop surface of a substrate according to a pattern stored in the patternmanagement system, wherein the first distribution of micro plasmas isformed in a gas mixture at least partially provided by the gas deliverysystem, the first distribution of micro plasmas corresponding to a firstportion of the pattern.
 2. The device of claim 1, further comprising aninstruction generator of the pattern management system connected to thepatterning head and to the position regulation system by a communicationbus, wherein the instruction generator is configured to generate atleast a first instruction and a second instruction, and wherein thepatterning head is configured to generate the first distribution ofmicro plasmas at a first position on the top surface of the substrateaccording to the first instruction, and a second distribution of microplasmas at a second position on the top surface of the substrateaccording to the second instruction, wherein the second distribution ofmicro plasmas corresponds to a second portion of the pattern, the secondportion being different from the first portion, and wherein the firstposition is different from the second position.
 3. The device of claim1, wherein at least one of the first or second distribution of microplasmas is formed from an array of electron emission structures of theelectron source.
 4. The device of claim 3, wherein at least a firstelectron emission structure at a first location of the array and atleast a second electron emission structure at a second location of thearray are configured to be activated independently according to at leastone instruction.
 5. The device of claim 2, wherein the electron emissionstructures comprise pyroelectric electron (PE) emission structures. 6.The device of claim 2, wherein the electron emission structures comprisethermionic electron emission structures.
 7. The device of claim 2,wherein the electron emission structures comprise field emission (FE)electron emission structures.
 8. The device of claim 4, furthercomprising an electron emission structure activation element configuredto receive at least one instruction and to activate or deactivateelectron emission structures at locations in the array according to theat least one instruction.
 9. The device of claim 2, further comprising apattern buffer configured to store at least a portion of the pattern,the instruction generator being configured to generate the instructionsbased on the stored portion of the pattern.
 10. The device of claim 5,further comprising an accelerating structure and a membrane of theelectron source, wherein the accelerating structure is configured todirect a beam of electrons from the at least one electron emissionstructure at a location of the array toward the membrane, and whereinthe membrane is configured to allow passage of the directed beam ofelectrons through the membrane into a working volume between thepatterning head and the top surface of the substrate.
 11. The device ofclaim 9, further comprising a voltage regulator configured to apply apositive voltage to the accelerating structure.
 12. The device of claim10, wherein the membrane is reinforced to withstand a pressuredifferential across the membrane between the first membrane face and thesecond membrane face.
 13. The device of claim 1, wherein the gas systemcomprises at least one orifice separate from the patterning head. 14.The device of claim 1, wherein the gas system comprises at least oneorifice configured to supply an atomized liquid to a working volumebetween the patterning head and a substrate.
 15. The device of claim 7,further comprising a vacuum source configured to form a pressuredifferential across the membrane, wherein the working volume containsthe gas mixture at a first pressure and an interior of the electron hasa second pressure smaller than the first pressure.
 16. The device ofclaim 3, wherein the plurality of electron emission structures includeare conductive structures selected from the group consisting of nanorods, nanowires, carbon nanotubes, fullerene-like structures, tunnelingcold field emitter cathodes, and pyroelectric material cathodes.
 17. Thedevice of claim 15, wherein the plurality of electron emissionstructures includes conductive materials selected from the groupconsisting of silicon, silicon carbide, and carbon.
 18. The device ofclaim 3, wherein the electron emission structure includes a diodestructure.
 19. The device of claim 1, wherein the electron emissionstructure includes a triode structure.
 20. A method of modifying asurface with a plasma, the method comprising: energizing a first set ofindividually addressable electron emission structures in an electronsource, the electron source having a membrane with a first surface and asecond surface; creating a blend of gases in a working volume adjacentto the second surface of the membrane, the second surface being on anouter surface of the electron source; accelerating electrons from thefirst set of individually addressable electron emission structurestowards the membrane; forming a first set of micro plasmas where theaccelerated electrons from the first set of individually addressableelectron emission structures intersects the blend of gases; andadjusting a distance between a substrate and the second surface suchthat the first set of micro plasmas intersects a top surface of thesubstrate at a first location.
 21. The method of claim 19, furthercomprising energizing a second set of individually addressable electronemission structures to form a second set of micro plasmas that intersectthe top surface of the substrate at a second location, wherein the firstset of micro plasmas has a first distribution of intersection pointswith the top surface, the second set of micro plasmas has a seconddistribution of intersection points with the sop surface points, and thesecond distribution is different from the first distribution.
 22. Themethod claim 20, wherein, upon forming the second set of micro plasmas,functionalization of the top surface at the first distribution ofintersection points with the top surface remains unchanged within anoverlap area of the top surface, the first distribution of intersectionpoints having a first perimeter on the top surface, the seconddistribution of intersection points having a second perimeter on the topsurface, and the overlap area falling within the first perimeter and thesecond perimeter.
 23. The method of claim 19 further comprisingmodifying a set of functional groups on the top surface of the substrateat the first distribution of intersection points or the seconddistribution of intersection points, and wherein the top surface outsidethe first and second distributions of intersection points does notundergo modifying a set of functional groups.
 24. The method of claim20, further comprising modifying the first distribution of intersectionpoints into the second distribution of intersection points while firstset of micro plasmas intersects the top surface of the substrate, upondisplacement of the substrate beneath the electron source.
 25. A methodof making a plasma device having an electron source, comprising:forming, in the electron source, an array of individually addressableelectron emission structures on an chip; placing, in the electronsource, an electron accelerating structure between the chip and a targetsubstrate; interconnecting the array of individually addressableelectron emission structures with a power supply and the electronaccelerating structure; placing, in a wall of the electron source, amembrane configured to pass a directed beam of electrons; positioning anozzle of a gas delivery system to deliver a flow of gas into a workingvolume between the electron source and the target substrate; andconnecting a controller element to the power supply configured toregulate an electrical potential between the array of individuallyaddressable electron emission structures and the electron acceleratingstructure.
 26. A arrangement of materials for generating spatiallyconfined plasma beams, wherein the arrangement comprises of, an array ofindividually addressable nanostructures on a substrate, an acceleratingstructure placed adjacent to the nanostructures, an electricalconnection between the nanostructures, a power supply, and theaccelerating structure, a membrane adjacent to the acceleratingstructure, wherein the membrane has a first face and a second face, atleast one nozzle near the second face of the membrane, wherein thenozzle allows for introducing gases forming a primed atmosphere nearsurface of the second face of the membrane, wherein when a potentialdifference is applied between the accelerating structure and thenanostructure array at least one directional electron beam is generated,wherein the directional electron beam penetrates through the membraneentering from the first face of the membrane and leaving through thesecond face of the membrane, wherein when the directional electron beamstrikes the primed atmosphere on the surface of the second face of themembrane a plasma beam is formed.